Girls aren’t boys. Girls are designed to psychologically and physically pair bond after sex, through the release of the hormone oxytocin.
This is a problem with girls, and women too, as they tend to aquire unhealthy attachment problems as they accumulate sexual partners, breaking (or losing) one attachment after another. There is research showing ongoing inability to pair bond the more sexual partners a woman has had. And IIRC its worse for women with an early age sexual experience.
Men on the other hand seem perfectly able to love them and leave them.
There are good reasons to think that human physiology is the underlying reason behind traditional sexual customs, which may have come about in a Burkean evolution.
But if a 26-year-old man had sex with a 17-year-old girl in your extended family, you'd want to string him up because she might be attached to him.